Chapter 10, Problem 6STP

To determine

To Choose: The correct option.

Answer to Problem 6STP

B. $-75\text{J}$

Explanation of Solution

Given:

The mass of the skater, $m=50.0\text{kg}$

The initial velocity of the skater, $v_i=2.0\text{m/s}$

The final velocity of the skater, $v_f=1.0\text{m/s}$

Formula used:

The kinetic energy of an object of mass m moving with velocity $v$ is given by,

  $KE=\frac{1}{2}m{v}^2$

Calculation:

Using the given values in above formula, the change in kinetic energy of the skater will be,

  $\begin{array}{c}\Delta KE=\frac{1}{2}m\left(v_f^2-v_i^2\right)\\ =\frac{1}{2}\left(50\right)\left({\left(1\right)}^2-{\left(2\right)}^2\right)\\ =-75\text{J}\end{array}$

Negative sign denotes that its velocity and thereby its kinetic energy decreases.

Conclusion:

Thus, the change in the skater’s kinetic energy is $-75\text{J}$ .